Recording device



May 12, 1959 G. FIRBANKS ETAL 2,886,650

RECORDING DEVICE v Filed oct. 22, 1952 4 sheets-sheet 1 May 12, 1959 G.FAIRBANKS ET AL 2,886,650

RECORDING DEVICE I, l Filed oct. 22, 1952 l y4 sheets-sheet 2 5/6NA L IN]zye 0715. Gran/Ll QL'I'MS,

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May 12, 1959 G. FAIRBANKS ET AL I 2,886,650

RECORDING DEVICE 4 Sheets-Sheet 5 Filed Oct. 22, 1952 May 12, 1959 G.FAIRBANKS ET Al.

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N u u Q D mtm L m. Mmmm mw MHD RECORDING DEWCE Grant Fairbanks andWilliam Littell Everitt, Urbana, lll., and- Robert Pierson Jaeger,Morristown, NJ., assignors to University of Illinois Foundation, acorporation of Illinois Application. October 22, i952, Serial No.316,289 10 Claims. (Cl. 179-1001) This-invention relates to a device forautomatically reproducing signals in a dilerent time than originallyproduced and more particularly to such a means for reproducinginformation, such as connected speech, in a shorter or longer time thanoriginally delivered without change in pitch that substantially aectsthe signal.

Ithasbeen known for example, that the human ear can 'accept connectedspeech at a much faster rate than the human voice can deliver it.lntelligibility of speech that is delivered much faster than originallyis not impaired so long as iidelity and frequencies are maintained as inthe original. It has also been found that comprehension of materialdelivered` at a much faster rate is easy for most persons. educationalbenefit in that a larger amount of materialy may be delivered to alistening audience in a much shorter time than ordinarily required. Ofcourse, the application commercially in radio broadcasting isimmediately apparent in that much more material could be given to thepublic in allotted time and that given material could bey altered. tooccupy an allotted time period.

.The basic function of the device to be described, is to takeinformation such as connected speech or sounds and reproduce them byleaving out small fragments or por-. tions. occurring during Very shorttime intervals. These fragments are so small in time duration that theydo not include a whole sound unit, or in other words, a whole syllableor even a sound in a syllable. What remains after the fragments arediscarded, is in eiect, squeezed together. The iinai recording is thusmade a continuous one from which the original speech `or sounds may beplayed back in a shorter time than required for the original delivery.The shortened materiai may sound much faster in delivery, but the pitchis unchanged and cornprehension iS still easily possible.

A particular embodiment of one device for accomplish-v ing the results`set out above is shown in the accompanying drawings, in, which.:

Figure l is a diagrammatic frontview of the apparatus;

'Figure 2 is a partially diagrammatic, broken, top plan.

view of the same apparatus;

Figure 3 is a diagrammatic, fragmentary, sectional view of. one of thepickup heads;

Figure 4 is a diagrammatic, fragmentary, side View of the pickupheadshown in Figure 3;

Fig. 5 is a schematic representation to show the relationship betweenthe multiple. head transducer and the recording ot messages therefromupon a moving record strip;

Fig. 6 is a schematic representation of one form of arrangement toreproduce recorded signal information following its recording, as forinstance by the apparatus of Fig. 5', v

. Fig.A 7 illustrates a modication of the strip contact region relativeto the multiple head transducer with the record tape strip being incontact with the drum for an arcuate space less than that correspondingto the arcuate spacing of adjacent respective transducers;

This brings to focus possibilities ofk 2,886,650 Patented May 12, 1959Fig. 8 is a diagrammatic and schematic representation to illustrateoperation of the apparatus for signal compression; and

Fig. 9 i`s a diagrammatic showing, generally similar t0. Fig. 8, to showthe expansion program.

The main purpose of the device of this invention is to sample discreteportions of a recording of connected speech and discard some of theportions so as to record less than the total number of portions. It isimportant that each discarded portion beso small' that a sound unitcould not be lost if that portion is discarded. The term sound uni asused herein, means any portion of an expression if missing, wouldinterfere with the intelligibility of the whole expression. In the caseof human speech, the discarded portions or intervals are so short thatwords and syllables are not lost in the shortening effect. Each sound isreproduced in sutlicient length to make it as intelligible as theoriginal sound, but enough of the sounds are omitted to greatly shortenthe time of delivery.

The particular means for accomplishing the instant purpose employs amagnetic recording tape 10 formed in the shape of a loop passing aboutcertain elements including idler wheels 1l and 12. The idler wheels aremounted in a relatively heavy metal bearing plate 13.l A drive mechanismincluding a driven wheel 14 clamps the loop of tape 10 against a rubbercovered pressure puck l5 to move the tape about the path formed by the,loop. In Figure 2, a driving shaft 17 is shown which is connected with avariable speed motor 16 for providing the driving power.

While a tape is shown as the recording element, it. should be understoodthat other magnetic recording ele.- ments or other nonmagnetic recordingelements could be used. The tape is driven in the direction of the arrow18 so that it passes rst over an erase head 19 and then to a record head20. Material from a microphone or from some other source is transposedby means of the record head 20 to the tape it). The material is thencarried over the idler wheel il to a transducer herein shown as a drum25 which has a number of pickup heads 26 positioned about its periphery.In the instant application the drum 25' has a pickup head 26 which mayhave a tip portion 27 extending through a slot 28 in the periphery ofthe drum so that it may pick up material recorded on the magnetic tape.

The drum 25 is separately driven by means of a shaft 30 which may beconnected to a separate variable speed motor 29, so that the speed ofthe drum may be regulated with relation to the linear velocity of thetape. Since there are four pickup heads 26 shown in the drum, the tapel() is in contact with the periphery of the drum for about so that onlyone pickup head will be taking material from the tape at a time. Thesampling and discarding of intervals is automatically accomplished bythe pickup heads in the drum. if the drum has a peripheral velocity lessthan the linear velocity of the tape, material will be taken from thetape by one head and then it Will quit reproducing and the succeedinghead will start to take material from the tape. At the instant when onehead leaves the tape and another starts to pick up, there is a physicaldistance on the tape between the two heads which is not recorded by anyof the heads in the drum. In other words, any material recorded on thetape i@ along this particular portion of the tape would be discarded andWill not be picked up by any of the pickup heads 26. Material that ispicked up, may be placed on another tape, Wire, disc or other record sothat it may be subsequently played. It will be noted that one or anotherof the pickup heads is continuously taking material from the loop ortape and therefore the record made of the material so picked up will becontinuous.

As an example, material may be placed on the tape which is moving at alinear velocity of 150 inches per second. (Lower speeds may be used inactual practice.) If it is desired to condense the material by 50%, orin other words, retain 50% of the material so as to be played in onehalf the time of delivery, the peripheral speed of the drum will bechosen so that the relative speed between the tape and pickup heads 26will be one half of 150 or 75 inches per second. The material picked upby the heads 26 may be fed to another recording tape moving at one halfthe velocity at which the tape is to be later played. In this manner thefrequencies are proper and the recording when played at the proper speedwill produce the connected speech in one half the time.

In order to choose the proper speed for the drum 25, it will be notedthat the relative linear velocity between the pickup heads and the tapeis equal to the fractional reduction in time desired. This means thatthe speed of the tape is equal to VT which is equal to d In where d isthe arcuate distance between heads on the drum in inches and ID is thediscard interval in seconds. The linear head velocity in inches persecond is VH which is equal to VTM-RR), where RR is the ratio ofretention, or the ratio of the retained material to the original. Whenthe device is used to condense material, the eiective velocity is thediiference between the tape and head velocities and when the device isused to expand material, the effective velocity is the sum of the twosince the head is reversed in direction. When the drum is rotatedoppositely in direction to the tape direction of movement, some of thematerial is repeated and will result in a final recording which has beenexpanded and would require longer time for play back than originaldelivery. The device may be worked in either manner and will provide arecord which may take either longer or shorter than original delivery.This latter view of the device may be important in the ield of languagestudy and elds such as voice correction.

In order to use the device for expanding either live material orrecorded material, the drum 25 is caused to rotate clockwise as viewedin Figure 1 while the tape proceeds in the direction of arrow 18. Theeffective velocity is thus the sum of VT and VH and as a result thefrequencies from the pickup heads are higher than those on the tape andcertain material will be repeated. The reproduction formed with thematerial picked up may be played at a slower speed to reestablish theproper frequencies and occupy a longer time.

In the modification of Fig. 5 the tape 10 is shown as traveling in thedirection indicated by the arrow at a velocity VT. In so moving the tapemay, illustratively, be driven by the puck 35 rotating in the directionshown by the arrow with the tape positioned between this drive puck andan idler 36. For illustrative purposes the tape is arranged in a loopform and passes over a second idler 37. Prior to any recording of soundor other intelligence information on the tape, the tape is erased by anystandard form of erase head such as that conventionally shown at 19which is activated by the indicated high frequency alternating currentsource.

Subsequent to tape erasure by the head 19 signal or intelligenceinformation is recorded by means of the record head 20 which receivessignals for recording which are supplied at a terminal 38 and thencethrough any standard form of recording amplifier apparatus,conventionally indicated at 39. Output signals from the amplilier 39control, in well known fashion, the signal information impressed orrecorded upon the magnetic tape.

As was indicated by the apparatus of Fig. 1, the drum 25 turns, forinstance, in the direction shown at a speed of VH (which represents headvelocity). The drum includes theI indicated four magnetic heads 26, oneof which is '4 shown adjacent to the tape at the position a. Energypicked up from the tape, and indicative of the intelligence forrecordings thereon scanned, is then supplied in well known fashion to astandard form of playback amplifier conventionally indicated 40 theoutput of which is supplied to recording amplifier 41. The recordamplifier 41 then provides for recording the information picked up bythe multiplicity of scanning heads 26 by the use of Va. record head 42similar to that shown at 20. The recorded information is then impressedupon the magnetizable tape or strip moving illustratively in thedirection of the arrow at a velocity VR (where VR is 4the velocity ofthe recording tape).

Following the recording of the information upon the tape strip 100 inorder to reproduce at an output point 45 that signal or intelligenceinformation which was supplied at point 38 the recorded information onthe tape 100 is translated (as shown by Fig. 6) in the region 100 by apickup head 43 positioned adjacent to the tape or strip 100 the outputfrom which at convenient times is fed into the playback amplifierconventionally represented 44 which is of standard characteristics andis then supplied as a signal output of the terminal point 45.

As was explained in an earlier part of the description, the tape whenbeing reproduced and scanned by the pickup head 43 moves by appropriatedrive means (not shown), illustratively, in the direction shown by thearrow at a velocity VR 1--Rc where VR is the case for the record head 42and represents the recording tape velocity, and Rc represents the ratioof compression.

For ease of reference and for a better understanding of the feature ofcompressing signals, the diagrammatic showing of Fig. 8 is provided. Inthis showing the Roman numerals indicate different initial positions ofthe multiplicity of recording heads 26 on the drum 25 relative to anassumed moving magnetic tape. The magnetic tape is assumed to be dividedinto a plurality of adjacent segments, each of a length corresponding tothe peripheral distance on the drum 25 carrying the multiplicity oftransducer heads 26 which separates any two adjacent heads 26. Thedesignations to the right of the figure indicate the segments of tapeand the recorded message. It can be assumed conveniently that positionscan be represented at ditferent positions of the clock and that thevarious transducer heads of the plurality 26 are designated by letters Athrough D. So considering Fig. 8, in part I, the segment 1 is shown at atime To when it irst comes into contact with the drum 25 and the rsttransducer head (shown as head A). At this moment it is intercepted bythe head A moving in the same direction as the tape, as explained inconnection with Fig. 5.

If it were to be assumed that the drum 25 were stationary, reproductionwould be on a one-for-one basis. if the velocity of the head rotatingwere equal to the velocity of the tape, of course, no signal could berepro duced because there would be no relative movement between thetransducer head and the tape. If, however, between the time periods Iand II it could be assumed that the head A moves through one-quarterrevolution, it will be apparent that during the same time period thetape will move, so that two complete tape segments, that is, tapesegment 1 and 2 pass at 9:00 oclock point where the head A rst contactedthe tape, which can bess sumed to have occurred at a time To. As aresult, head A reproduces segment 1 during such time interval and theeffective velocity of the tape is then Viv-VH, where VT is the tapevelocity and VH is the head velocity.- In the assumed condition of Fig.8, VH, as already explained in the foregoing material, is assumed to beequal to Za. z

assassin l which equals the eiective velocity of the tape. Consequently,the frequencies' of segment 1" of the tape as reproduced by the head Aare divided'l by two;

Considering now the time II, it' will be seen that the head1 A hasrotated inthe direction of the arrow to the 6:00 oclock position and thehead B has arrivedy at the 9:00 oclock position', with the tape segment2' lying between these two heads and in contact with the drum. At thistime head A is about to leave its position of contact with the tape,while head B is about tobegin reproducing because it contacts the tapeat the third tape segment. Accordingly, there is noA discontinuity inthe reproduction, although segment 2 ofl the tape' is not reproduced byany head.

The remaining diagrams of Fig; 8 show how' the process continues andwith the assumed conditions' theA assumed odd numbered segments of thetape are reproduced at reduced frequency and even numberedy segments ofthe tape are discarded although there is complete continuity of messagereproduction.

In the diagram to the right of the schematically` represented multipletransducer heads and the tape the smaller blocks indicate tape segments,as assumed, and the larger blocks indicatev the tape segments being re'-produced by the related transducer head. The relative enlargementbetween the lengths ofthe rectangles schematically designates theproportional frequency reduction occasioned by the operation explained.In this connectiony it will be seen that between the times I andy II,for example, segment 1 is reproduced by head A in the same time which isnecessary for both segments 1 and 2 to pass any given point. Followingthisy the head B reproduces segment 3 at the same rate, and so on: As tothe duration of the odd numbered segments these may be` termed samplingintervals. Movement, accordingly, by the plan described will bring aboutfrequency compression or reduction.

The showing of Fig. 9 is a generally similar diagram to that of Fig. 8but is for the purpose of showing the expansion process, as against thecompression process of Fig. 8. As is depicted by Fig. 9 the drumcarrying the several transducer heads A, B, C, and D is arranged to turnor revolve in the direction opposite to that at which the tape moves,each of whichy direction, is shown byy the-arrow adjacent either to thedrum or to the tape itself. In the illustrated condition of Fig. 9 theexample is selected where the velocities are equal so that the effectivevelocity is equal` to their sum.

On this showing at the timeA To shown at tape segment 1 the segment islinx contact with. the drum between the heads A and D. During the nextinterval the head D, as it moves from the indicated 6:00 oclock positionas per Part I to the 9:00 oclock position will reproduce both segments 1and 2 and then leave the tape. At this time the tape will be reproducedby the head C which is moved to the 6:00 oclock position to interceptthe tape at the beginning of segment 2. This will then reproducesegments 2 and 3 during its sweep. The result is shown to the right ofthe gure and indicates that between the times I and II while segments 1and 2 are passing the 6:00 oclock point segments 1, 2, 2 and 3 arereproduced.

The remaining portion of Fig. 9 similarly shows how the processcontinues. From this it will be apparent that since the effective tapevelocity with respect to the transducer head has been increased by theopposite movement of the head and the tape, frequency multiplication hasbeen provided. The original frequencies then are restored by reproducingthe processed message in an appropriate longer time period. One hundredtimes the amount of time thus added divided by the original time isknown as the expansion percentage. By the diagram of Fig. 9 it will benoted that this equals 100%.

A condensed recording may be formed by using the multiple head of thepresent invention as record heads as contrasted to pickup heads as setout above. The heads are capableof interchangeable action andy verylittle need be done to the apparatus to change its function. For thispurpose, as represented by Fig. 7, four heads 26 arey shown, similar toFig. 1, and with this number, a tape 10", not iny a loop, is passed incontact with the drum 25 for an angular distance of 360/ 8 or 360dividedE by twice the number of heads. The direction of head revolutionis opposite to the direction of movement of the tape so that each headslowly backs up along the tape. Since with four heads, for example, thetape contacts the drum for 45 there will be sorne time while no head isin contact with the tape to record the materiali that isl simultaneouslyfed to the four heads. During this period, the tape moves forwardly tobring the point Where thepreceding head quits recording into properregistry for the next. head. to start recording Without leaving aphysical gap on the tape. The resultant' tape is a shortened recordingof the material fed to the multiple heads. The discardedI material isthat whichv occurred during the intervals when no head was in con, tactwith the tape.

In some instances, it may be desirable to operate the apparatus as aninterrupter. In order to accomplish this function, the heads 25 arehooked up as record heads` to place the material fed to them on a tape10'. The heads 25 and tape are caused to move in the same direction withthe heads at. slower linear velocity so that the material recorded onthel tape is separated by physical gaps equal in length to the arcuatedistance between the heads 25.

Experiments have. shown that connected speech may be` reproduced in thetime of original delivery without substantial change. If only 50% of thematerial is retained, a noticeable speed-up of delivery is present whilecomprehension and.y intelligibility remain. The limit to which connectedspeech may be reduced in delivery time will be dependenty uponcomprehension rather than the ability to remove enough small timeintervals to produce a shortened'y record. In all of the recordsfidelity and frequencies are retained as in. the original delivery.

The foregoing detailed description has been given. for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, for some modiiicationsv will be obvious to those skilled` intheV art.

We claim:

1'. A device for automatically reproducing sounds in a different timethan the original deliveryl without. sub.- stantial change in pitch,comprising, an, impulse recording element having the sounds recordedthereon, an irnpulse pickup device having a plurality of pickup heads,means providing relative movement between the recording element andpickup device, said pickup device being positioned for sequential andcontinuous pickup of intermittent portions of the recorded sounds at afrequency diierent from the original frequency at which recorded, and arecord element for receiving the picked-up portions for subsequent audioreproduction, and means to reproduce the record at a different rate ofspeed to return the frequencies to the original level.

2. A device for automatically reproducing signals in a different timethan the original production time without substantial change in pitch,comprising, a moving impulse recording strip element and a transducerhaving multiple pickup elements adapted consecutively to pick upimpulses from intermittent portions of the strip element in continuousform for recording on another recording element and means for drivingthe strip element past the transducer at a relative speed to change thepitch of the impulses picked up.

3. A device for automatically reproducing sounds in a diiferent timethan the original delivery without substantial change in pitch,comprising, a magnetic recording tape adapted to be driven at apredetermined rate, a recording head in proper position to record thesounds on the moving tape, a drum having a plurality of pickup 1 headstherein positioned with respect to the tape to consecutively take'thesounds from the tape, and means f or driving the drum at a peripheralvelocity at variance .with

the velocity of the tape whereby the materiai `picked up i 2 .by thedrum recording heads when recorded on a separate record element may takeaditferent time lfor playback than the original deivery.

i 4. A device asspeciiied-in claim .3 wherein the velocity of the tapeis equal to i .ID where d is the arcuate distance in inches betweenpickup heads and ID is the discard interval in seconds of time.

5. A device as specied in claim.3 wherein the druml carries the pickupheads in opposite direction to move- .-ment of. the. tape whereby someof the recorded sound units are reproduced more'than'oncei l 6. A devicefor automatically reproducing stantial change inA pitch, comprising, .a.continuous .loop of magnetic recording tape, a drive for moving thetape in the path formed by said loop at predetermined speed greatly in'excess' ofl the. normal. recording rate-,a recording head positionedadjacent to the tape to record the sounds thereon, a drum positionedadjacent to the path of the tape beyondl said .recording.head, said drumhaving a plurality of pickup heads therein each positioned 'to .take thesounds from the tape when the tape is against the drum andadjacent .toone of .the heads, said tape -con-.

sounds in a different time than the original delivery without sub- Cil9. A devicefor lreproducing sound recorded .on-a tape in a diterenttimefrom the original delivery time of the lsound, without substantialchange in pitch, comprising means for moving the tapezin*lapredetermined path. at a rate greatly in excess of the normal play rateof the' tape, :and a circular rotatable pick-up device positioned i in adilerent time from the original delivery time of the sound, withoutsubstantial change in pitch,` 'comprising tacting an arc of the drumsufficient to permit only onepickup. head at a time to take soundstherefrom, means for driving thedrumataperipheral speed'diereut-from thespeed of the moving tape,- and means for continuously 1 recording thesounds from the drum pickup heads.

7.- A device .for reproducingsounds in a different time than originaldelivery without substantial change ini pitch, comprising means fordelivering a tonal message,

means for. directly receiving the. tonal message, means for reproducingthe tonal message at a pitch 'greatly dif# ferent from the originalpitch of the message, means for altering intermittently at very smallintervals of time the number of tonal units in the message withoutaffecting the audible content of the message, and means for receivingthe pitch-altered and content-altered message and means for reproducingthe message at the original pitch during a dilerent delivery time.

8. Apparatus as set forth in claim 7 in which the means for varying thepitch of the original message is independent of the proportional timechange in the message.

adjacent to the path of thetape andl having multiple piclo up headsthereon, means for rotating the pick-up device to bring the pick-upheads consecutively into contact with the tape ata speed differentfromzthe-speed of` the tape,

means for recording upon arecord element the successive picked up.portions ata dilerent pitch, the rate of movement of the pickup device.with respect to .the .movement of the tape being such as to alter thesound content of .the pickedup `message in a predetermined ratio, and

means lfor moving .the recording element at a. speed relative to itsnormal playing speed which is a reciprocal of r said predeterminedratio, whereby the original pitch may be reproduced by lplaying .therecording element at its normal speed.

10 A device for reproducing sound recorded on a tape means for .movingthe tape in a predetermined path, a

circular :rotatable pick-up .device adjacent the path of the tape havingmultiple pick-up heads thereon', means' for rotatiugtl1epick-up deviceto bring the pick-up heads "consecutively into Contact with-the-tape`ata speeddif-` ferent from the speed of the tape, means for recordingupon arecord element the successive picked up portions at a differentpitch, the rateo `movement of the pick-.up

device with respect to the movement of `the tapeibeing such as to alterthe sound content of the picked up message; in a :predetermined ratio,-andmeans for moving the recording element at a speedrelative toitsnormall play-` I l ing speed which is a reciprocal of said predetermined:ratio Awhereby the. Original pitch may. be reproduced `by playing therecording element at its normal speed.l l

.References Cited in theiile of this patent UNITED STATES PATENTS1,671,151 French et al May 29, 1928 1,996,958 Freund Apr. 9, 19352,115,803 Dudley May 3, 1938 2,170,751 Babrilovitch Aug. 22, 19392,352,023 Schuller June 20, 1944 OTHER REFERENCES A.I.E.E. Journal, vol.93, part III, 1946, pp. 453-454.

